The Sonoma County Board of Supervisors on Tuesday could take the next step in a long-proposed plan to add fluoride to most of the county’s drinking water.

The move is intended to improve dental health and is a common practice across the country, recommended by leading national and international health agencies. But it has sparked emotional protests from a wide range of opponents concerned about health implications and other issues.

The county has been studying the proposal for a year. A feasibility report examining health and legal issues is due out Thursday and will be the subject of a public meeting Friday, from 3:30 to 5 p.m. at a county health office at 3313 Chanate Road in Santa Rosa.

Rita Scardaci, the county’s health services director, said on Wednesday that the report does not make any “definitive recommendation” on the introduction of fluoride.

But county health officials continue to back that move, pointing to what they’ve called an oral health “crisis” among Sonoma County children, especially those from low-income families.

The Board of Supervisors last February backed study of water fluoridation as a key way to address the problem.

On Tuesday the board is set to consider approving the next step: a six-month, $103,000 study of the engineering changes necessary to fluoridate local drinking water.

The 2:10 p.m. hearing is likely to draw a large crowd, and pit supportive health officials against skeptics and activists who oppose the practice.

Water fluoridation has been backed by the Centers for Disease Control and Prevention, the U.S. Surgeon General, the World Health Organization and the American Dental Association, which called it “the single most effective public health measure to prevent dental decay.”

Almost three-quarters of the nation’s population served by public water systems — or about 196 million people — are receiving fluoridated water.

State law requires the practice for all public water suppliers in California with more than 10,000 connections. The unfunded 18-year-old statute has not been widely enforced.

Critics, including non-traditional health advocates, property rights activists and some environmentalists, have urged the county to reject water fluoridation. They’ve voiced concerns about government-imposed medication and health impacts on humans and on wildlife exposed to fluoridated wastewater.

Currently in Sonoma County, the only fluoridated water is delivered to residents of Healdsburg and the adjacent Fitch Mountain area.

The proposal would add fluoride to water used by nearly three quarters of the county, including 350,000 residents served by the Sonoma County Water Agency in Windsor, Santa Rosa, Rohnert Park, Cotati, Petaluma, Sonoma and the Valley of the Moon.

The Sonoma County Water Agency also serves about 250,000 residents in Marin County. Of those customers, 185,000 people in south and central Marin — residents from Marinwood to Sausalito — already get fluoridated water. The roughly 65,000 residents who don’t currently get fluoride — but who would under any Water Agency introduction — live in western and northern Marin County, including Novato.

Presentations at the Friday meeting will be given by Scardaci, Silver Chalfin, and Oscar Chavez, executive director of the Community Action Partnership, the anti-poverty nonprofit group.

Public comment is scheduled for 4:05 p.m.

Public comment will also be taken at the Tuesday Board of Supervisors’ meeting.